1. Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for transmitting data and control information in a wireless communication system.
2. Related Art
In next generation multimedia wireless communication systems, which have been actively studied in recent years, there is a demand for a system capable of processing and transmitting a variety of information (e.g., video and radio data) at a higher data rate in addition to the early-stage voice service. The wireless communication system is designed for the purpose of providing reliable communication to a plurality of users irrespective of their locations and mobility. However, a wireless channel has an abnormal characteristic such as a fading phenomenon caused by a path loss, noise, and multipath, an inter-symbol interference (ISI), a Doppler effect caused by mobility of a user equipment (UE), etc. Various techniques have been developed to overcome the abnormal characteristic of the wireless channel and to increase reliability of radio communication.
A multiple input multiple output (MIMO) scheme is used as a technique for supporting a reliable high-speed data service. The MIMO scheme uses multiple transmit antennas and multiple receive antennas to improve data transmission/reception efficiency. Examples of the MIMO scheme include spatial multiplexing, transmit diversity, beamforming, etc. A MIMO channel matrix depending on the number of receive antennas and the number of transmit antennas can be decomposed into a plurality of independent channels. Each independent channel is referred to as a spatial layer or a stream. The number of streams is referred to as a rank.
In general, the wireless communication system is a multiple access system capable of supporting communication with multi-users by sharing available radio resources. Examples of the radio resource include a time, a frequency, a code, transmit power, etc. Examples of the multiple access system include a time division multiple access (TDMA) system, a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access (SC-FDMA) system, etc.
SC-FDMA may have a lower peak-to-average power ratio (PAPR) or cubic metric (CM) while having almost the same complexity with OFDMA. When the PAPR is low, a transmitter can effectively transmit data by avoiding a non-linear distortion duration of a power amplifier. Since the low PAPR is advantageous to the UE in terms of transmit power efficiency, the SC-FDMA is adopted in uplink transmission in 3rd generation partnership project (3GPP) long term evolution (LTE) as disclosed in the section 5 of 3GPP TS 36.211 V8.2.0 (2008-03) “Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation (Release 8)”. The 3GPP LTE standard defines only single-stream transmission by using only a single transmit antenna.
Meanwhile, there is an ongoing standardization effort for an international mobile telecommunication-advanced (IMT-A) system aiming at the support of an Internal protocol (IP)-based multimedia seamless service by using a high-speed data transfer rate of 1 gigabits per second (Gbps) in a downlink and 500 megabits per second (Mbps) in an uplink in the international telecommunication union (ITU) as a next generation (i.e., post 3rd generation) mobile communication system. A 3rd generation partnership project (3GPP) is considering a 3GPP long term evolution-advanced (LTE-A) system as a candidate technique for the IMT-A system. It is expected that the LTE-A system is developed to further complete an LTE system while maintaining backward compatibility with the LTE system. This is because the support of compatibility between the LTE-A system and the LTE system facilitates user convenience. In addition, the compatibility between the two systems is also advantageous from the perspective of service providers since the existing equipment can be reused.
Improvement of an uplink maximum transfer rate is significantly emphasized among requirements of the LTE-A system. This is because it is difficult to satisfy the maximum transfer rate required by the IMT-A system when using only SC-FDMA employing the single transmit antenna. A system considered for transfer rate improvement is a system in which the MIMO and the legacy SC-FDMA are combined.
Accordingly, there is a need for a method and apparatus for effective data transmission in a multi-antenna system.